Zhejiang Sankai Mechanical and Electrical Co., Ltd

Harmonic Reducer

What is Harmonic Reducer



A harmonic reducer is a mechanical device that is commonly used in various industrial applications to reduce the speed and increase the torque of an input shaft. It is a type of gear mechanism that incorporates a series of flexspline, wave generator, and circular spline components. The unique design and operation of a harmonic reducer allow it to achieve high-torque output with exceptional precision and efficiency.


Advantages of Harmonic Reducer



Compact Size and Lightweight Design: Harmonic gear reducers are known for their small size and lightweight characteristics. This makes them ideal for applications where space is limited or where weight constraints are critical. Such design helps to reduce the overall dimensions and weight of mechanical processing equipment, thereby enhancing flexibility and portability.


High Transmission Precision: Harmonic gear reducers maintain precise transmission ratios even under varying load conditions, which is crucial for mechanical processing applications that require accurate positioning and control. This high precision feature is particularly beneficial in precision machine tools and automated equipment.


High Load Capacity: Despite their compact size, harmonic gear reducers can handle relatively high loads, thanks to their unique internal structure design, such as the interaction between the rigid and flexible gears. This high load capacity makes harmonic gear reducers suitable for various heavy-load mechanical processing environments.


High Transmission Efficiency and Smooth Motion: Due to their working principle, harmonic gear reducers can maintain smooth motion at high input speeds, reducing vibration and noise. This is essential for precision and surface quality control during the mechanical processing process.


Strong Adaptability: Harmonic gear reducers can operate in a variety of working environments, including enclosed spaces or harsh conditions, giving them an edge in special mechanical processing scenarios. 


Why Choose US



Our Factory
Zhejiang Sankai Machine and Electric Co.,Ltd is an integrative and professional manufacturer of power transmission device, which specialize in scientific research, production and marketing.


Adopting advanced detecting equipment and means, company establishes a quality control system that is in accordance with 1S0900 I: 2015. Products are sold all over the country, exporting to Southeast Asia, Europe, America and other regions. Sankai will continue, as we always do, to strive to become a leader of power transmission industry.


Our Products
Our company specialize in High Precision Planetary Gearbox, NMRV series Worm Gearbox, UDL series Stepless Speed Variator, SRC series Helical Gearbox, SKM series Helical-Hypoid Gearbox, Precision Gearbox for Robot Arm and PC Helical Gear Unit.


Quality services
Sincerely Sankai determine to provide service of better quality, in-time and fast reply to our clients. And Sankai is looking forward to cooperating with domestic and foreign friends and grow together with our hard work and professionalism.


Strain Wave Drive


What Are the Basic Components of Harmonic Reducer

The harmonic reducer is an important part of the robot, and is generally used in the forearm, wrist or hand of the robot. With the increase of labor costs in my country, the trend of robots replacing labor is becoming more and more obvious, and the advantages of products produced by robots with good consistency and high assembly accuracy are also more and more valued by manufacturers.
Therefore, the demand for robots in my country is also increasing. As one of the important components of robots, the demand for harmonic reducers is also increasing.
The harmonic reducer is mainly composed of three basic components, namely the wave generator, the flexible wheel and the rigid wheel.
Wave generator: Composed of flexible bearings and elliptical cams.
Flexible wheel: Thin-walled metal elastomer part with outer gear ring.
Rigid wheel: A rigid annular part with an inner gear ring, generally 2 more teeth than the flexible wheel.
The wave generator rotates continuously, forcing a point on the flexible wheel to change its position continuously. At this time, at any point of the pitch circle of the flexible wheel, along with the angular movement of the wave generator, a symmetrical harmonic wave is formed. , so it is called a harmonic reducer. When it is used, the wave generator is usually active, the rigid wheel is fixed, and the flexible wheel is output.


The Application Field of Harmonic Reducer

Harmonic reducers are extensively used in robotics for precise positioning of robotic arms, grippers, and other actuators. Their high precision and torque density make them ideal for applications that require accurate control and repeatability.


Aerospace and Defense
In aerospace, harmonic drives are used in satellite deployment mechanisms, solar panel positioning, and antenna pointing systems. Their high torque output and compact size are advantageous in space applications where weight and space are critical.


Medical Equipment
Harmonic drives are used in medical equipment such as surgical robots, diagnostic imaging systems (CT, MRI), and prosthetics. The smooth and precise motion control they provide is essential for accurate medical procedures and patient comfort.


Automation and Manufacturing
In the manufacturing sector, harmonic reducers are used in assembly lines, CNC machines, and automated guided vehicles (AGVs) for precise control of machine movements. They ensure high precision and reliability in repetitive tasks.


Energy Sector
Harmonic drives are used in solar tracking systems to maintain the optimal positioning of solar panels throughout the day. They also find applications in wind turbines for precise control of the yaw and pitch systems.


Security and Surveillance
In surveillance systems, harmonic reducers ensure smooth and accurate panning and tilting of CCTV cameras, providing high-resolution images with minimal vibration.


Automotive Industry
Harmonic drives are used in power steering systems, active suspension systems, and manufacturing equipment within the automotive industry. They provide the high torque and precision required for these applications.


Precision Instruments
In precision instruments such as telescopes and microscopes, harmonic reducers ensure smooth and accurate focusing and positioning mechanisms.


Metrology and Measurement
In metrology equipment, harmonic reducers provide the precision and stability required for accurate measurements and calibrations.


Entertainment Industry
In the entertainment industry, harmonic drives are used in animatronics, flight simulators, and other motion platforms for smooth and realistic motion simulation.


Comparing RV Reducer with Harmonic Reducer


Harmonic reducer is used for industrial robots with small load, or several shafts at the end of large robots. Harmonic reducer used for small robots is characterized by small size,light weight, large bearing capacity, high motion accuracy and large single-stage transmission ratio.

Harmonic reducer is one of the harmonic transmission devices, which includes accelerator and reducer. The main structure of harmonic reducer is rigid wheel, flexible wheel, bearing and wave generator,
all of which are indispensable. Among them, the number of teeth of the rigid wheel is slightly larger than that of the flexible wheel.


RV reducers are often used in robot joints with large torque, especially in leg, waist and elbow joints, industrial robots with heavy load, and RV reducers are used in the first, second and third axes. Compared with harmonic reducer, RV reducer has higher fatigue strength, stiffness and service life. The disadvantages of harmonic reducer include that with the increase of service time, the motion accuracy will decrease. Contrary to the advantages of light weight and small size of harmonic reducer, RV reducer has the disadvantages of heavy weight and large overall size.


Both of them are engaged with less tooth difference, but the difference is that one of the key gears in harmonic is flexible and needs repeated high-speed deformation, so it is fragile. Therefore, compared with RV reducer, harmonic reducer has lower bearing capacity and shorter service life. RV reducers generally use cycloidal pinwheels, while harmonics used to use involute teeth. Now some manufacturers use double circular arc teeth, which is more advanced than involute teeth.


Compared with harmonic reducer, RV reducer is a new transmission product. RV reducer is actually developed on the basis of traditional needle-and-thread pin-wheel reducer, which not only overcomes the shortcomings of general needle-and-pendulum transmission, but also has more advantages, such as long service life, stable accuracy, high efficiency, smooth transmission and so on, small size, light weight and large speed change ratio range.


Installation Method Of Harmonic Reducer
Strain Wave Drive
Strain Wave Harmonic Gear
Harmonic Drive Strain Wave Gear
Strain Wave Gear Reducer

① Fix the reducer on the output flange, and then connect the input fixing flange to the rigid wheel.

② Apply lubricating grease evenly on the flexible bearing, and inject 80% lubricating grease into the cavity at position A (please use the specified lubricating grease, do not replace the grease randomly to avoid damage to the reducer). Install the wave generator on the input motor shaft or connecting shaft, and connect and fix it with screws and flat washers.

③ Install the reducer according to the direction, aligning the long axis of the wave generator with the long axis direction of the reducer flexible wheel. Once in place, fix the reducer with the corresponding screws, and tighten the screws slightly.

④ Set the motor speed to around 100 rpm, start the motor, and tighten the screws in a crisscross manner, increasing the locking force corresponding to the screws in equal increments of four to five times. All connecting and fixing screws must be of grade 12.9 and coated with thread sealant to prevent screw failure or loosening during operation.

⑤ First, evenly apply a layer of lubricating grease on the inner wall of the flexible wheel, and then inject lubricating grease into of the flexible wheel, with an injection amount of approximately 80% of the flexible wheel cavity. (Please use the specified lubricating grease and do not replace it randomly to avoid damage to the reducer.)

⑥ The machining requirements for the installation plane connected and fixed to the reducer: flatness of 0.01mm and verticality of the axis of 0.01mm, and concentricity of threaded holes or through holes with the axis of 0.1mm.


Precautions for Using Harmonic Reducer

Gear wear
The reducer operation load is too large or long-term impact on the gearbox, installation eccentric or poor size coordination, poor lubrication will cause abnormal wear between the parts, thus affecting the performance accuracy of the harmonic drive.

Due to the improper selection and installation of the harmonic reducer, excessive load, the superposition of the inherent vibration coefficient and the body resonance, the Angle error will be further amplified, the accuracy of the bearing will be insufficient, resulting in the flexible wheel and the rigid wheel in the engagement operation will lead to the vibration of the harmonic gear drive.

The abnormal sound
There are foreign bodies in the harmonic wave reducer, insufficient lubrication, the installation position of the wave generator does not meet the requirements, and the improper installation and interference of the internal parts will produce abnormal sound during operation.

Strain Wave Reducer

Diagnosis method of strain wave gearbox


Strain Wave Reducer

Observation and analysis of sound and vibration
Speed reducers failure usually produces abnormal sound and vibration. Through careful observation and analysis of the characteristics of these sounds and vibrations, the type of failure can be tentatively determined. First of all, judge the source of sound, and eliminate the abnormal noise vibration caused by motor problems. If it is a relatively sharp abnormal sound in operation, it is necessary to check the bearing problems and check whether the bearing rotation is stuck and stagnant.

Check the lubrication
The lubrication condition of the strain wave drive is crucial to its normal operation. Check the lubricant for cleanliness, viscosity and grease filling to ensure that the lubrication system works properly. If metal particles are found in the lubricating oil, the bearing or gear may be damaged.

Check the gear wear condition
Gear is the core component of harmonic gearbox and also one of the sources of common faults. The most direct method is to first judge whether there is an obvious gap in the reducer, if there is an obvious gap, you can determine the wear inside the wear of the gear, including tooth surface wear, tooth surface peeling, tooth bottom wear, etc., can determine whether there is a gear fault.

Perform a diagnostic test
After confirming the possible faulty parts, some special fault diagnosis tests can be conducted, such as vibration analysis, temperature measurement, oil analysis, etc. These tests can provide more detailed and accurate fault diagnosis results and help determine the specific cause of the failure.

Maintenance of Harmonic Reducer



Proper Installation
Alignment: Ensure that the input shaft of the motor is precisely aligned with the harmonic drive's input. Misalignment can lead to premature wear and reduced lifespan.
Mounting: Follow the manufacturer's guidelines for mounting the gearbox. An unstable or improper mount can cause unnecessary stress on the gears.

Regular Inspection
Visual Checks: Regularly inspect the gearbox for any visible signs of damage, leaks, or loose components.
Vibration: Excessive vibration can indicate an issue with the alignment or balance of the drive system. Use a vibration analyzer if necessary.


Type: Use the lubricant specified by the manufacturer. The wrong type can affect the performance and lifespan of the gearbox.
Level: Check the lubricant level regularly and top up or change as required. Low lubrication can lead to increased wear and potential failure.


Load Management
Avoid Overloading: Ensure that the harmonic drive is not subjected to loads beyond its rated capacity. Overloading can cause damage to the gears and other components.
Start-Up: When starting the system, do so gently to avoid sudden, high loads that can stress the gearbox.


Temperature Control
Operating Temperature: Keep the operating temperature within the recommended range. Excessive heat can reduce the effectiveness of the lubricant and accelerate wear.


Maintenance Schedule
Scheduled Maintenance: Follow a regular maintenance schedule as recommended by the manufacturer. This typically includes periodic checks, lubricant changes, and part replacements.
Cleaning: Clean the gearbox and its surroundings regularly to prevent contamination, which can affect performance and lead to premature wear.


Training and Operation
Operator Training: Ensure that operators are trained in the correct use and handling of the harmonic drive gearbox to prevent misuse and potential damage.
Understanding Specifications: Operators should understand the specifications and limitations of the gearbox to avoid overloading or misapplication.


Replacement and Repair
Component Replacement: Replace worn or damaged components as soon as they are identified to prevent further damage to the gearbox.
Professional Repair: For major repairs or when in doubt, consult with a professional or the manufacturer to avoid incorrect repairs that can affect performance.



Q: What are harmonic reducers?

A: The Wanshsin harmonic reducers are gearboxes based on the so-called strain-wave principle in which a flexible tooth ring rotates via an oval drive shaft in an annular outer tooth ring. Because the outer ring has more teeth than the flexible inner ring, the rings will move relative to each other in relative terms.

Q: What is the purpose of a Harmonic Drive?

A: Harmonic Drive, mechanical speed-changing device, invented in the 1950s, that reduces the gear ratio of a rotary machine to increase torque. It operates on a principle different from that of conventional speed changers.

Q: What is a harmonic actuator?

A: The ever increasing demands on servo actuation require perfect chemistry between the motor, gear, sensor and controller. Harmonic Drive® Servo Actuators are a combination of highly dynamic compact servo motors, precision gears and integral tilt resistant high load capacity output bearings.

Q: What is the Harmonic Drive mechanism?

A: Harmonic drives are among the best in terms of these criteria [1-18]. This type drive principle of operation is based on the engagement of rigid and deformable flexible gear wheels. Deformation process is provided by wave generator. Flexible wheel is a ring or a thin shell.

Q: What is the difference between harmonic reducer and RV reducer?

A: The RV reducer has higher fatigue strength, stiffness and life, unlike the harmonic drive, the movement accuracy will be significantly reduced as the use time increases, and its disadvantages are heavy weight and large dimensions.

Q: What is a harmonic in a pipe?

A: Different amounts of a wavelength in a pipe will result in a different frequency being heard. Because these are the frequencies of the waves that will naturally resonate in the pipes, we call them the resonant frequencies. In music, you might have heard these referred to as harmonics.

Q: What is the importance of harmonic?

A: Simple harmonic motion is important in research to model oscillations for example in wind turbines and vibrations in car suspensions.

Q: What are the advantages of Harmonic Drive?

A: With operating principles and construction that maximize output torque and minimize size and weight, gears offer advantages such as high reduction ratios in a single stage, zero backlash, and high precision that cannot be equaled by conventional gear trains.

Q: Can you backdrive a Harmonic Drive?

A: Backdriving Harmonic Drive gearing can be easily backdriven unless the input shaft is locked. Under no circumstances should a gearhead be used to support a load without a failsafe device on the output if there is risk of personal injury.

Q: How are harmonic drives made?

A: The harmonic drive, which is composed of a circular spline, a wave generator and a flexspline, is a compact, light-weight, and precise torque transmission mechanism with little backlash. From these components, the flexspline is the key element for motion transmission.

Q: Do harmonic drives have backlash?

A: Has a full array of small, zero backlash gears and actuators. Perfect for semiconductor and robotics.

Q: How is a Harmonic Drive different from a cycloidal drive?

A: There is simple no way the harmonic drive can handle that amount of torque as the cycloidal drive. The flex spline walls are just too tin and the PLA material too week. In terms of durability, it's the same thing. The cycloidal drive can last much longer than the harmonic drive.

Q: How does a motor reducer work?

A: Located between a motor and a piece of machinery, a speed reducer lowers the speed delivered by the motor such that an application can make use of the motor's energy. In a speed reducer, a set of large and small gears work together to lower the input speed while increasing the torque.

Q: What is the function of the reducer in a motor?

A: Speed reducers or gearboxes are used to reduce motor rotation speed and increase output torque, which is equivalent to improve the working capacity of the motor. In addition, the output direction change is available through a speed reducer.

Q: Why is harmonics a problem?

A: Depending on your electrical power system, there are a lot of places where harmonics can cause inefficiencies. In a manufacturing setting, unmanaged harmonics can increase motor temperatures by 10 degrees to maintain output. This side effect can reduce the life of a motor by 50%.

Q: How do harmonics affect motor efficiency?

A: In addition, voltage and current harmonics can affect the torque developed. More, harmonics in rotating machinery can cause vibrations and noises. Negative sequence harmonics cause negative torque which opposes the fundamental motor torque, thus causing a decrease of the global motor efficiency.

Q: How do you control harmonics?

A: By increasing the impedance of the supply circuit, the harmonic current is limited. Installation of harmonic suppression reactors on capacitor banks increases the impedance of the reactor/capacitor combination for high-order harmonics. This avoids resonance and protects the capacitors.

Q: How to reduce harmonics in a power system?

A: One simple method is to add an inductor to the input of the VFD. This inexpensive solution will help reduce harmonic content from higher than 60% down to the 40% range. Designers can also use harmonic mitigating transformers to reduce power-system harmonics.

Q: How do harmonics affect motors?

A: Harmonic content makes it harder to magnetize the copper and iron in the motor's stator and rotor, causing higher eddy current and hysteresis losses. If harmonic frequencies exceed 300 Hertz, the skin effect compounds these losses. Second, all these extra losses manifest as additional heat.

Q: What is the efficiency of Harmonic Drive?

A: Efficiencies as High as 90% Measured on actual shaft-to-shaft losses rather than tooth losses (as with other gearing), standard Harmonic Drive gearing efficiencies are normally in the 80-90% range.

As one of the most professional harmonic reducer manufacturers and suppliers in China, we're featured by quality products and competitive price. Please rest assured to buy harmonic reducer for sale here from our factory. Contact us for quotation and free sample.

Worm Gearbox, Precision Planetary Gear Reducer, Strain Wave Drive